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A Photo-Micrographic Camera. 

 Bt J. D. Hardt. 



(Read September 15th, 1893.) 



It is often very desirable to photograph an object as it is seen 

 under the microscope without disturbing it or having to alter 

 any of the arrangements. For this purpose I have devised this 

 instrument, which I exhibited at the R.M.S. three years ago, 

 but as it was not reported or figured, and I have been frequently 

 asked for a description, I take the opportunity of having it 

 here this evening to show it and explain its various parts. 



Referring to the diagram, which is a vertical section made to 

 a working scale, A is a flat piece of cedar (cigar box) wood 



2|in. square, having a circular hole cut in it l^in. diameter. 

 This is the plate-holder. Along three of its sides runs a flange. 

 B, is a cone made of stiff (or brown) paper 2in. long, having an 

 opening at the bottom of lin. diameter, and glued to the top, to 

 the under side of the flat, by its flange. All the parts should 

 be painted dead black. Inserted and fixed at the bottom of the 

 cone is a double concave lens, C, having a negative focus of 

 9in., though other lenses having a deeper curvature may be 

 employed. 



A cardboard cover or lid is made to tit loosely over the top of 

 the plate-holder to keep out the light during exposure. 



To use it. The object having been focussed, the eye-piece is 



